W25Q64BV Datasheet, PDF (29/61 Pages) Winbond – 64M-BIT SERIAL FLASH MEMORY WITH DUAL AND QUAD SPI

W25Q64BV
11.2.13 Fast Read Quad I/O (EBh)
The Fast Read Quad I/O (EBh) instruction is similar to the Fast Read Dual I/O (BBh) instruction except
that address and data bits are input and output through four pins IO₀, IO₁, IO₂ and IO₃ and four Dummy
clocks are required prior to the data output_. The Quad I/O dramatically reduces instruction overhead
allowing faster random access for code execution (XIP) directly from the Quad SPI. The Quad Enable bit
(QE) of Status Register-2 must be set to enable the Fast read Quad I/O Instruction. To ensure optimum
performance the High Performance Mode (HPM) instruction (A3h) must be executed once, prior to the
Fast Read Quad I/O Instruction.
Fast Read Quad I/O with “Continuous Read Mode”
The Fast Read Quad I/O instruction can further reduce instruction overhead through setting the
“Continuous Read Mode” bits (M7-0) after the input Address bits (A23-0), as shown in figure 13a. The
upper nibble of the (M7-4) controls the length of the next Fast Read Quad I/O instruction through the
inclusion or exclusion of the first byte instruction code. The lower nibble bits of the (M3-0) are don’t care
(“x”). However, the IO pins should be high-impedance prior to the falling edge of the first data out clock.
If the “Continuous Read Mode” bits (M7-0) equals “Ax” hex, then the next Fast Read Quad I/O instruction
(after /CS is raised and then lowered) does not require the EBh instruction code, as shown in figure 13b.
This reduces the instruction sequence by eight clocks and allows the Read address to be immediately
entered after /CS is asserted low. If the “Continuous Read Mode” bits (M7-0) are any value other than
“Ax” hex, the next instruction (after /CS is raised and then lowered) requires the first byte instruction code,
thus returning to normal operation. A “Continuous Read Mode” Reset instruction can be used to reset
(M7-0) before issuing normal instructions (See 11.2.29 for detailed descriptions).
Byte 1 Byte 2
Figure 13a. Fast Read Quad Input/Output Instruction Sequence Diagram (M7-0 = 0xh or NOT Axh)
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Publication Release Date: July 08, 2010
Revision E